Aerodynamic performance optimization of the archimedes spiral wind turbine: combined experimental and CFD analysis of step ratio and blade number effects

This study presents an integrated numerical and experimental investigation of the aerodynamic performance of the Archimedes Spiral Wind Turbine (ASWT) under wind speeds ranging from 5 to 10 m/s. The analyses were conducted at a Reynolds number (Re) of approximately 9.6 × 104, with the operational range of the tip speed ratio (TSR) varying between 0.5 and 3. The study focuses on examining the combined effects of step ratio ($${\text{S}}_{1} /{\text{S}}_{2}$$) and blade number on the energy conversion efficiency of ASWT. A series of ASWT rotor models was designed using SolidWorks 2020 and analyzed through three-dimensional simulations in ANSYS CFX 2020 R2, with results validated experimentally under controlled wind tunnel conditions. To isolate the effect of $${\text{S}}_{1} /{\text{S}}_{2}$$, configurations ranging from 0.05 to 0.45 were examined while maintaining a constant aspect ratio (L/D). The analysis identified the intermediate configuration (PR-5) as the most aerodynamically efficient model. This configuration was subsequently adopted to evaluate the influence of blade number, which varied from two to six blades, to assess its impact on rotor solidity, torque generation, and flow stability. The three-blade model based on the PR-5 geometry (PR-5–3) demonstrated the best overall performance, achieving a maximum power coefficient ($$C_{p}$$) of 0.264 at a TSR of 1.88, while the two-blade configuration (PR-5–2) showed relatively better adaptability at higher TSR. These findings provide a structured framework for optimizing ASWT geometry and blade configuration to enhance aerodynamic performance and operational reliability in low-speed and multidirectional wind environments.